Apparatus and method for coaxially aligning two rotatable shafts

ABSTRACT

An apparatus and method for aligning two coaxially coupled rotatable shafts. A servo operated multi axis positioning device is movable along a longitudinal axis parallel to the axis of the shafts, and movable vertically to position a laser range (LRF) adjacent to the two shafts, which measures the distance between the LRF and a spot on the shafts. A controller having a processor and memory communicates with the positioning device and the LRF to collect data at two axial positions on each shaft. At each position the LRF measures the distance to the shaft and stores the measurement and location data. The LRF is vertically repositioned and the measurement and storing steps are repeated over a scan distance sufficient to provide enough data to determine the location of the shaft center. The processor then calculates and compares the shafts centerlines and determines the necessary adjustments needed to move the shafts into coaxial alignment.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part of U.S. application Ser. No.16/915,728 filed Jun. 29, 2020, which claims the benefit of U.S.provisional application Ser. No. 62/869,768 filed Jul. 2, 2019, thedisclosures of which is hereby incorporated in its entirety by referenceherein.

TECHNICAL FIELD

This application relates to an apparatus and a method for coaxiallyaligning two rotatable shafts, particularly shafts of a rotary machine,such as a pump and a motor, connected by a rotary coupling.

BACKGROUND

When two rotatable shafts are coaxially coupled together it is veryimportant to minimize coaxial misalignment. Even a small amount ofmisalignment can result in power losses, unnecessary bearing loads andpremature coupling failure. Accordingly, the shafts must be carefullyinitially aligned and periodically inspected and adjusted as necessary.

Motor driven pumps used in municipal water systems and in sewagecollection and treatment facilities are typical users of large motor andpump pairs which must be maintained in proper coaxial alignment.Further, many industrial and chemical facilities use very large motorand pump pairs, turbines and generators, motors and compressors, andother co-axially aligned rotatable machines which need to be maintainedin proper coaxial alignment.

Various devices have been used to align two coaxial rotatable shafts inthe past ranging from traditional mechanical surface plate gauges to alaser and a detector mounted to adjacent shafts to be inspected whilethe shafts are manually rotated as illustrated in U.S. Pat. No.8,533,965.

SUMMARY

An apparatus and method for aligning two coaxially coupled rotatableshafts is provided. Alignment can be, and is preferably, measured whilethe shafts are rotating in their normal operating condition. A base ispositioned adjacent to the shafts to be aligned. The base supports aservo operated positioning device which is movable along a longitudinalaxis parallel to the axis of the shafts, and movable to verticallyposition spots on the shaft measured by a laser range finder (LRF)adjacent to the two rotatable shafts. The LRF measures the distancebetween the LRF and a spot on the shaft. A controller having a processorand memory communicates with the positioning device to cause the LRF toscan a plurality of spots on the shafts spaced over a vertical range andcollects data at two or more axial positions on each shaft. At eachposition the LRF measures the distance to the shaft and stores themeasurement and location data. The spot measured by the LRF isvertically repositioned and the measurement and storing steps arerepeated over a scan distance sufficient to provide enough data todetermine the location of the shaft center. The processor thencalculates and compares the shaft centerlines and determines thenecessary adjustments needed to move the shafts into alignment.

An exemplary embodiment of the apparatus for aligning two rotatableshafts has a base which is positionable adjacent to two rotatable shaftswhile they are coaxially coupled together and rotating. A servo operatedpositioning device is attached to the base, movable along a longitudinalX-axis parallel to the axis of the rotating shafts, and movablevertically along a Y-axis. A laser range finder (LRF) is affixed to thepositioning device and spaced a distance from the two rotating shafts,to measure the distance between the LRF and a spot on the rotatingshafts parallel to a Z-axis. A controller is provided which communicateswith the positioning device and the LRF. The controller has a processorprogrammed to position the LRF at a first axial location on a first oneof the rotating shafts, measuring distance to the shaft and stores themeasurement and spot location data. The controller verticallyrepositions the LRF and repeats the measurement and data storage steps.Vertical repositioning and measurement steps are repeated until enoughdata is collected to determine the location of the shaft center at thefirst axial location. The processor is programmed to reposition the LRFat a second X-axis location on a first one of the rotating shafts andthe Y-axis scan is repeated and the location of the first shaft axis iscalculated. The processor is programmed to reposition the LRF at a thirdand fourth X-axis location on a second one of the rotating shafts andthe Y-axis scan is repeated and the location of the second shaft axis iscalculated. The alignment of the two shafts axes are compared. Theprocessor then determines the adjustment of one of the two shafts thatis necessary to move the shafts in to coaxial alignment.

Another exemplary embodiment of the apparatus for aligning two rotatableshafts has a base which is positionable adjacent to two rotatable shaftswhile they are coaxially coupled together and rotating. A servo operatedpositioning device, in the form of a multi axis robotic arm, is attachedto the base, movable along a longitudinal X-axis parallel to the axis ofthe rotating shafts. The robotic arm has an end which is movable alongat least the Z and Y axes using servo motors or other means ofelectronic positioning. Preferably, the robotic arm also operates alongthe X axis as well. A laser range finder (LRF) is pivotably affixed tothe end of the robotic arm to measure the distance between the LRF and aspot on the rotating shaft. A controller is provided which communicateswith the robotic arm and the LRF. The controller has a processorprogrammed to position the LRF at a first axial location on the firstone of the rotating shafts. The robotic arm positions the LRF adjacentto the rotating shaft to measuring distance between the shaft and theLRF. The LRF measurement and the LRF location on the robotic arm end isused to determine and store location data of a spot on the shaftperipheral surface. The controller repositions the robotic arm and theLRF to measure a different spot on the peripheral surface and repeatsthe measurement and data storage steps. The repositioning andmeasurement steps are repeated until enough data is collected todetermine the location of the shaft center at the first axial location.

The processor is programmed to reposition the LRF at a second X-axislocation on a first one of the rotating shafts and the scan is repeatedand the location of the first shaft axis is calculated. The processor isprogrammed to reposition the LRF at a third and fourth X-axis locationon a second one of the rotating shafts and the scan is repeated and thelocation of the second shaft axis is calculated. The alignment of thetwo shafts axes are compared. The processor then determines theadjustment of one of the two shafts that is necessary to move the shaftsin to coaxial alignment.

A method for aligning two rotating shafts which are coaxially coupledtogether is disclosed which includes providing a positioning deviceattached to a base to be placed adjacent to the shafts to be aligned.The positioning device has a holder movable along a longitudinal axisparallel to an axis of two axially coupled rotating shafts, and movablevertically to position a laser range finder (LRF) affixed to thepositioning device and spaced a distance from the two rotating shafts.The LRF measures the distance between the LRF and a plurality ofvertically spaced spots on the rotating shafts. A controller, having aprocessor and memory, is provided which communicates with the LRF and auser interface. The LRF is positioned at a first axial location on afirst one of the rotating shafts, the controller communicating with theLRF to measure distance to a spot on the shaft and stores themeasurement and spot location data. Data is collected at a minimum ofthree spot locations or until enough data is collected to determine thelocation of the shaft center at the first axial location. This processis repeated at a second X-axis location on the first shaft and at athird and fourth X-axis location of the second shaft. The processor thencalculates the centerline of the two shafts using stored measurement andspot location data using a best-fit circle algorithm to define the axisof the two shafts and then determines the adjustment of one of the twoshafts needed to move the shafts in to proper alignment.

In the robotic arm embodiment, the LRF is moved in both the Z and Ydirections. Preferably the LRF axis is oriented perpendicular to theshaft axis prior to making measurements.

In an alternative embodiment the diameter of the shaft is known or ismeasured and input into the processor. With the shaft diameter known itis only necessary to collect data at a minimum of two Y-axis locations.

In yet another embodiment rather than vertically moving the LRF, the LRFis located at the approximate shaft center height. The beam of LRF thenpivots about an axis generally parallel to the shaft to scan a pluralityof measurements at one or more Y-axis locations. The pivoting LRF canalso be used in a system of unknown shaft diameters if data is collectedat three Y-axis locations.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top view of an alignment apparatus adjacent a motor drivenpump;

FIG. 2 is a side view of the alignment apparatus of FIG. 1;

FIG. 3 is a sectional view taken along line 3-3 of FIG. 2;

FIG. 4 is an enlarged section of FIG. 3 showing the laser range finder(LRF) scanning motion;

FIG. 5 is a histogram of the data collected at one scan point;

FIG. 6 is X-Y plot of the average scan data at one shaft position towhich a circle is fit in order to locate the shaft center;

FIG. 7 is a block diagram of the use of the alignment apparatus toperform the shaft alignment method;

FIG. 8 is a schematic of the components making up the alignmentapparatus.

FIG. 9 is an alternative embodiment of the alignment apparatus havinglaser range finder (LRF) with a pivoting scanning motion;

FIG. 10 illustrates the location of the centerline of a shaft of knowndiameter using two points on the shaft surface;

FIGS. 11A and 11B are a top views of an alternative alignment apparatusembodiment adjacent a motor driven pump:

FIG. 12 is a perspective view of a multi axis robotic arm;

FIG. 13 is a side view of the multi axis robotic arm;

FIGS. 14A and 14B are views showing the effect of LRF misalignment withthe shaft;

FIG. 15 is another alternative alignment apparatus embodiment adjacent amotor shaft;

FIG. 16 is a top plan view of the alignment apparatus embodiment of FIG.15;

FIG. 17 is a X-Y plot of the average scan data at three positions on theshaft.

DETAILED DESCRIPTION

As required, detailed embodiments of the present invention are disclosedherein; however, it is to be understood that the disclosed embodimentsare merely exemplary of the invention that may be embodied in variousand alternative forms. The figures are not necessarily to scale; somefeatures may be exaggerated or minimized to show details of particularcomponents. Therefore, specific structural and functional detailsdisclosed herein are not to be interpreted as limiting, but merely as arepresentative basis for teaching one skilled in the art to variouslyemploy the present invention.

The disclosed preferred embodiment of the apparatus 10 and the methodare used to calculate the adjustments necessary to realign two coupled,rotatable shafts which are inspected while “hot and rotating” in asteady state operating condition. The two shafts are typicallyassociated with a large co-axially aligned rotating machines such asmotor and pump pairs, turbines and generators, and motors andcompressors, and other co-axially aligned rotating machines. which needto be maintained in proper alignment. While a motor M and pump P aredescribed in this preferred embodiment the claims are not limited to anyspecific types or size of co-axially aligned rotating machines.Similarly, the disclosed example is oriented horizontally however theapparatus and method could also be used in machines of otherorientations such as a vertical turbine and generator. The apparatus andmethod can be used on the two shafts when not rotating but it has beenfound that more practical results can be achieved while the shafts arerotating.

In the sample embodiment shown in FIG. 1 motor M drives the pump P. Thepump shaft 12 is typically part of a pump assembly P, that is coupled toinlet and outlet pipes and for all intents and purposes is immovable andwill remain “stationary”. The motor shaft 14 is part of a motor assemblyM and is coupled to the pump shaft 12 by a pair of couplings 16, 18 andone or more flexplates 20. Slight adjustments to the position of themotor M can be made by loosening the bolts 22 holding the motor feet 24to the foundation 26 and shifting the motor by shimming the motor feet.Great care is taken to align the two shafts in all dimensions beforeturning on the motor. Shims 28 are placed under four feet 24 of themotor M to adjust the height (Y-axis), and adjustment screws 30 (shownin FIG. 3) are used to move the motor in-and-out laterally (Z-axis).

The apparatus 10 computes the amount of adjustment necessary toreposition the motor feet along the Y-axis and Z-axis to realign the twoshafts by measuring shaft location while the motor and pump is “hot androtating”.

FIG. 1 illustrates a top plan view of a large electric motor M connectedto a pump P. A side view is shown in FIG. 2 illustrating the positioningapparatus 10 relative to the motor and pump and the various measurementlocations. Apparatus 10 conducts a measurement scan of at least fouraxially spaced locations, two on the pump shaft and two on the motorshaft. The measurements are made using a non-contact laser range finder(LRF) 30. The LRF is attached to a positionable base 32 adjacent to themotor M and pump P as shown. The LRF is movable relative to the motoraxis by a multi axis positioning device. An X-servo 34 connected to abase 32 moves the LRF parallel to the motor axis. The LRF is movablevertically in the Y direction along a vertical column 36 by a Y-servo 38connected to the X-servo 36.

As illustrated in FIG. 3 the LRF measures the distance between the LRFand the pump shaft 12 at point PS. Optionally the LRF is provided withlevel sensor with a micro level adjustment servo 40 to maintain the LRFand the produced laser output beam exactly horizontal. Another optionalfeature is a Z-axis servo 42 enabling the LRF to be positioned close tothe rotating surface, maintaining the scan distance to less than 2inches, preferably less than 1 inch. By minimizing the Z distancemeasurement accuracy can be significantly improved by selecting a LRFhaving a short range.

The following input parameters are input into the controller 44 via auser interface before running the alignment scan. Note that X-axisrefers to left-and-right in above FIGS. 2 & 3, Y-axis to up-and-down inFIG. 2, and Z-axis to in-and-out best seen in FIG. 1.

PSx: X-position on pump shaft (or similar), closest to pump

PCx: X-position on pump side of coupling (or similar)

MCx: X-position on motor side of coupling

MSx: X-Position on motor shaft (or similar), closest to motor

MF: distance from inside edge of pump coupling to front feet on motor

MR: distance from inside edge of pump coupling to rear feet on motor

LE: distance from laser reading point PCx to inside edge of pumpcoupling

As previously stated, the pump P should be considered stationary.Therefore, the imaginary centerline of the pump shaft is the foundationused for all calculations. The motor M must be moved through shims 28and adjustment screws 30 to align or realign with the pump.

First, the X-values for PS, PC, MC, and MS are entered into the system,typically by moving the LRF (through the User Interface UI) to thepreferred positions and storing these X-values. Once the scan isinitiated, the laser scans the surface (up and/or down) at PSx and PCxas shown in FIG. 4, collecting thousands of data points on the surfaceof the shaft or coupling. At each data point hundreds of readings aremade, preferably at least 200, and an average or mean of the readingsare stored. Optionally, the lowest and highest readings are discarded toimprove accuracy however a number of other techniques can be used toimprove accuracy of the stored data point. The Y-servo 38 moves the LRFto the next reading site and another average or mean data point isstored. Preferably the X movement increment is over 3 inches, and morepreferably over 4 inches.

The Y-servo in the illustrated embodiment has a travel of 1.0 incheswhich is sufficient for many commonly used shaft sizes. Ideally theY-servo scan distance is at least 20%, preferably over 20% and less than50% of the radius of the rotating section being scanned. When used onlarge diameter shafts and couplings the scan distance increasesaccordingly. The scan is done while the motor is on and the shafts arerotating and have reached a steady state operating condition. Thecollected averaged scanned measurements at each point PS, PC, MC, and MSare evaluated programmatically in a Z-Y diagram as shown in FIG. 6. Thisseries of data points form a curved circular segment 42 to which acircle is fit to using a best-fit algorithm. Preferably, 50 to 250 datapoints make up the circular segment. However, it is possible to fit acircle to as few as three data points as illustrated in bold in FIG. 6.

Using a best-fit-circle algorithm, such as Levenberg-Marquardt, thecenter point 40 of the shaft can be calculated in three dimensions, atboth PSx and PCx. The best-fit circle 44 has a center point 40 whichdefines a point on a line representing the axis of the shaft, asillustrated in FIG. 6. These points provide two absolute points inthree-space (PSx, PSy, PSz) and (PCx, PCy, PCz). Two 3D points defines a3D line, and this line determines the pump shaft centerline. More thantwo points could be used as well, meaning additional intermediate pointsbetween PS and PC. In this case, a best-fit-line algorithm, such asleast squares, may be used to determine a more precise centerline,however two points is satisfactory.

Important outputs from the algorithms include the pump pitch (Y-axisslope) and the pump yaw (Z-axis slope) relative to apparatus 10,computed from (PCy−PSy)/(PCx−PSx). Pump yaw is computed from(PCz−PSz)/(PCx−PSx). Note there is no need for the pump or apparatus tobe perfectly level since all measurements are relative. We now have two3D points, that define an imaginary centerline in three dimensions thatextends from the pump through the motor. Next, we can align the shaft 14of the motor M to match the pump shaft 12 in all three dimensions.

Scanning the motor shaft 14 is done similar to the scanning of the pumpshaft 12. The LRF scans the motor shaft 14 or the motor coupling 18, orat two or more spaced apart X-axis points (i.e. MCx, MSx, etc.) andcomputes at least two center points MCx, MCy, MCz and MSx, MSy, MSz andthe resultant motor centerline which is best fit using a best-fit-linealgorithm. Like with the pump, the motor's relative pitch(MSy−MCy)/(MSx−MCx) and yaw (MSz−MCz)/(MSx−MCx) are computed for themotor's centerline. Even after precise “cold” alignment, the motorcenterline is typically out of alignment with the pump centerline once“hot and running”. To be in near-perfect alignment, the motor must beshut down and the feet adjusted (up/down and in/out) so that itscenterline is aligned with the centerline of the “stationary” pump.

We have computed the two 3D points that define the pump shaftcenterline. We have also computed the pump pitch and yaw relative to theapparatus. To align the two shafts, we need to make the motor pitch andyaw the same as the pump pitch and yaw, and that the two shaft axesintersect at the coupling connecting the shafts together. A translation(up/down, in/out) may also be required of the motor shaft in addition toadjusting the pitch and yaw to obtain proper co-axial alignment. Forboth MC and MS, we can compute the ideal 3D coordinates that would putthe motor shaft in perfect alignment with the pump shaft. We will callthese ideal coordinates MCx, MCyi, MCzi and MSx, MSyi, MSzi.

It should be noted that the 3D alignment problem can be broken down intotwo, 2D alignments, namely up/down and in/out (the motor is not adjustedleft/right once coupled to the pump). First, we will discuss theadjustment calculations in the Y-axis (i.e. pitch alignment) andseparately the adjustment calculation for the Z-axis (i.e. yawalignment). We are solving for how much to adjust the feet of the motorsuch that the two center points at MCx, MCyi, MCzi and MSx, MSyi, MSzifall perfectly on the imaginary extended centerline projected out fromthe pump.

Pitch Calculation: A 2D line can be described by the equation y=mx+b,where m is the pitch and b is the y-intercept. For pump pitch, we havetwo baseline points PSx, PSy and PCx, PCy which can be used to computethe perfect pitch m=(y2−y1)/(x2−x1) and the y-intercept (b=y−mx). With mand b known, we can compute the ideal (i.e. aligned) y-value (yi) forany x-value, specifically at MCx and MSx. This provides us with MCx,MCyi and MSx, MSyi.

Yaw Calculation: Similarly, we can represent the pump's 2D yaw line withthe equation z=nx+c, where n is the yaw and c is the z-intercept. Forpump yaw, we have two baseline points PSx, PSz and PCx, PSz which can beused to compute the perfect yaw n=(z2−z1)/(x2−x1) and the z-intercept(c=z−nx). With n and c known, we can compute the ideal (i.e. aligned)z-value (zi) for any x-value, specifically at MCx and MSx. This providesus with MCx, MCzi and MSx, MSzi.

By combining the results from the ideal pitch and yaw calculations, wenow have 3D coordinates MCx, MCyi, MCzi and MSx, MSyi, MSzi, and anyadditional points in between. These are where the motor center pointsneed to be in order for the two shafts to be in perfect alignment, andtypically vary from MCx, MCy, MCz and MSx, MSy, MSz which is where theywere measured to be.

Calculating the difference between the existing, measured motor centerpoints MCx, MCy, MCz and MSx, MSy, MSz and their ideal, alignedlocations MCx, MCyi, MCzi and MSx, MSyi, MSzi is simple subtraction. Theonly complication is that the motor feet adjustments are not directlybelow MC and MS. Instead, the adjustments are some distance away whichcreates a “lever arm” at MF and MR.

However, we can use a simple ratio to determine the amount of adjustmentat some point further away. We know the distance from PS-to-MC is(PSx−MCx). We also know the distance from PS-to-MF is ((PCx−PSx)+LE+MF).If the second distance is twice the first, for example, then we mustdouble the amount of adjustment at the front foot. Similarly, we knowthe distance from PS-to-MR is ((PCx−PSx)+LE+MR). If the distance to MRis three times the distance to MC, for example, then we must triple theamount of adjustment at the rear foot. This is true for both pitchadjustments (i.e. shims) and yaw adjustments (screws 30).

The apparatus uses precise positioning of the laser along the X-axis,surface scanning in the Y-axis using a LRF making high-precision laserdistance measurements in the Z-axis and precise incrementalrepositioning of the laser along the Y-axis to establish a baselineposition for the pump and motor shaft surfaces. Outliers are filteredfrom the raw data and the best available measurement data is run througha best-fit-circle algorithm to determine two or more center points foreach shaft. Adjustments to the motor feet are then calculated, and themotor can be put into near perfect alignment with the pump. No otheralignment system can measure alignment of a motor and pump shaft while“hot and running” or align two shafts to this level of precision.

The basic components of the measurement apparatus 10 are illustratedschematically in FIG. 8. The apparatus 10 has a controller 50 having aprocessor 52 and a memory 54 for controlling the movement of the LRF,possessing the collected data, calculating the position of the pump andmotor shafts and calculating the necessary movement to co-axially alignthe shafts. The controller is coupled to the X-servo 34, the Y-servo 38and to a user interface UI. The UI, which can be a keyboard and monitorof a touch screen, enables the user to cause the controller to positionthe LRF at the four data collection positions PS, PC, MC, and MS beforethe start of the measurement procedure. Alternatively, the UI can be alaptop computer, a smart phone or tablet. Preferably the X-servo movesthe LRF between the four PS, PC, MC, and MS. However, in a low-costembodiment the LRF could be manually moved along the base on a precisiontrack and positioned at stops precisely located at the four spaced apartmeasurement locations. In even a lower cost point apparatus the Y-servocould be replaced with a mechanical screw and guide way similar to thatuse in a lathe or other machine tools to manually position the LRF atthree or more precisely spaced apart locations enabling a best-fit curveto be fit to the three points in order to define the shaft center.

The method for aligning two rotating shafts which are coaxial coupledtogether is shown in block diagram in FIG. 7. The method comprises thesteps of:

providing a positioning device attached to a base, having a holdermovable along an X-axis parallel to an axis of two axially coupledrotating shafts, and movable along a Y-axis to position a laser rangefinder (LRF) affixed to the holder a paced a distance from the tworotating shafts to measures the distance between the LRF and a pluralityof vertically spaced spots on the shafts|

providing a controller, having a processor and memory, communicatingwith the LRF and a user interface|

positioning the LRF at a first X-axis and Y-axis location on a first oneof the rotating shafts, causing the controller communicating with theLRF to measure the Z-axis distance to a spot on the shaft and storingthe measurement and spot location data;

repositioning the LRF along a Y-axis, and repeating the measurement,storing, steps at least until enough data is collected to determine thelocation of the shaft centerline at the first axial location;

positioning the LRF at a second X-axis location on the first rotatingshaft, causing the controller to measure distance between the shaft andthe LRF and storing the measurement and spot location data

repositioning the LRF along the Y-axis and repeating the measurement,storing steps and repeating until enough data is collected to determinethe location of the shaft centerline at the second X-axis location

positioning the LRF at a third X-axis location on a second one of therotating shafts, causing the controller to measure distance between theshaft and the LRF and storing the measurement and spot location data

repositioning the LRF along the Y-axis and repeating the measurement,storing steps and repeating until enough data is collected to determinethe location of the shaft centerline at the third axial location

positioning the LRF at a fourth axial location on the second rotatingshaft, measuring causing the controller to measure distance between theshaft and the LRF and storing the measurement and spot location data

repositioning the LRF along the Y-axis and repeating the measurement,storing steps and repeating until enough data is collected to determinethe location of the shaft centerline at the fourth axial location; and

calculating in the processor the centerline of the two shafts at each ofthe four X-axis locations using stored measurement and spot locationdata using a best-fit circle algorithm to define two spaced apart axislocation points for each shaft and determining the adjustment of one ofthe two shafts needed to move the shafts in to coaxial alignment andoutputting the adjustment information to the user via the userinterface.

In another embodiment, shown in FIG. 9, rather than vertically movingthe LRF, the LRF is positioned in a fixed located at the approximateshaft center height. The beam of LRF is then pivoted over an angle θabout an axis generally parallel to the shaft to scan a plurality ofY-axis locations. Pivoting the LRF causes the laser beam emitted fromthe LRF to measure a spot on the rotatable shafts to move in the Ydirection relative to the rotatable shafts. The shaft centerline is thendetermined as described above or as described in the followingparagraph.

In another an alternative embodiment the diameter of the shaft is knownin advance or is measured and input into the processor. When the shaftdiameter is known it is only necessary to collect data for at least twoY-axis locations. The center location of a known diameter shaft can bedetermined with only two points as shown in FIG. 10. If the twomeasurement points are the same distance from the LRF dimension thedistance between the points is the chord length C of a line extendingthrough the shaft. A line through the LRF and the center of chord C goesthrough the center of the shaft as illustrated in FIG. 10. With theradius R known the shaft center can be located relative to the LRFposition using simple algebra, the Pythagorean theorem, geometry, andthe chord length equation. Alternatively, the two points can be used tolocate the shaft center by fitting a known diameter arc to the twopoints. When the shaft diameter is known, much less data needs to becollected and the circle fitting calculations are greatly simplified.

In another embodiment of the apparatus 60, shown FIG. 11-14, the servooperated positioning device, is provided by a multi axis robotic arm 62which provides another type of multi axis positioning device. Therobotic arm 62 is affixed to a base 64 stationarily located relative tothe axes of the rotating shafts to be aligned. The robotic arm 62 ismade up of a lower member 66 attachable to the base 64 in one or morefixed locations. Preferably, atop the lower member 66 is a swivel plate68 rotatable about a vertical 1^(st) axis by a 1^(st) servo motor.Pivotably attached to swivel plate 68 is a proximal end of lower arm 60.The proximal end of lower arm 70 is rotatable about a 2^(nd) axis,preferably parallel, to the swivel plate 68 by a 2^(nd) servo motor. Thedistal end of the 1^(st) arm is pivotable attached to the proximate endof an upper arm 72 and rotated about a horizontal 3^(rd) axis by a3^(rd) servo motor. The distal end of the upper arm 72 is pivotablyconnected to a LRF and rotatable about a horizontal 4^(th) axis by aservo motor. Preferably the LRF is rotatable about a 5^(th) axisperpendicular to the 4^(th) axis by a 5^(th) servo motor. The 5^(th)axis enables the beam of the LRF to maintain a perpendicular position tothe shaft after moving in an X-direction between two t spaced axialshaft locations without moving the robot lower member 66 along base 64.

The servo motors in the robotic arm enable the LRF to be preciselylocated in space and be circumferentially moved about the shaft. Thelaser beam formed by the LRF can be oriented perpendicular to the shaft.The use of a robotic arm enables the LRF to be located relatively closeto the shaft, preferably within 40 mm, and more preferably with 20 mm,resulting in a high degree of accuracy. Of course, the multi axisrobotic arm embodiment of the apparatus 60 can be used in the manner ofthe apparatus embodiments disclosed in FIGS. 1-10, where the distancefrom the LRF and the spot on the shift being measure is not heldconstant.

FIG. 11 is a plan view of robot arm 62 attached to base 64 whichlaterally positioned relative to motor M and pump P having a pair ofgenerally coaxial shafts 12′ and 14′ interconnected by a coupling C. Therobotic arm 62 is positioned on the base 64 outboard of the shaft 12′ ofpump P. Preferably robot arm 62 can reach both the first and secondX-axis location where measurements are taken. Alternatively, the robotarm 62 can be repositioned on the base 44 outboard using an X-axisservo. When propagating the movement of the LRF between X-axis locationscare should be taken to avoid striking the LRF or the robot arm on theshafts, the coupling or any safety guards. Optionally a vision systemhaving a camera or LIDAR sensor coupled to the controller to monitor theposition of the LRF and the robot arm relative to the surroundings toavoid a strike.

The robot arm 62 mounted on carriage 63 can be moved along the base 64,as shown in FIGS. 11A and 11B, to a position outboard of the motor Mshaft shown in phantom outline. From this position robot arm 62 canreach both the third and fourth X-axis locations. Alternatively, therobotic arm 62 mounted on carriage 63 can be repositioned on the base 64outboard using an X-axis servo. By moving the robotic arm 62 betweenmeasurements at the first and second and third and fourth X-axislocations the arm can remain generally perpendicular to the shaftminimizing the need to adjust the position of the LRF about the 5^(th)axis to be perpendicular to the shaft.

FIG. 12 is an example of a servo operated multi axis robotic arm 62which is attachable to a base 64 for supporting a laser range finder(LRF) on the arm distal end (free end). The robotic arm distal end ispivotably attached to a laser range finder (LRF) to orient the LRFperpendicular to and space a distance from the rotating shaft to beingmeasured. The LRF measures the location of a plurality of peripherallyspaced spots on the shafts at two axial positions on each shaft.

FIG. 13 is a side cross-sectional elevation of multi axis robotic arm 62with the LRF positioned in close proximity to the shaft to be measured.In order to achieve high accuracy, The LRF is preferably within 40 mm,and more preferably with 20 mm of the shaft. The LRF is moved about theperiphery to a plurality of positions as illustrated. To locate theshaft center at least three spots on the shaft periphery must bemeasured. If the shaft diameter is known only two spot need to bemeasured. For accuracy purposes many more spots are measure to betterfit a curve to the data. Preferably, at least 10 spots are measured over45 degrees of the shaft circumference. More preferably, over 200 spotsare measured over 90 degrees of the shaft circumference for bestaccuracy.

FIG. 14A illustrates a slight LRF misalignment from the idealperpendicular alignment to the shaft. This will result in the section ofoval shape, shown in exaggerated form. Once the LRF is aligned in aperpendicular manner as shown in FIG. 14B the cross section is circular.The 5^(th) axis servo motor at the arm distal end enables the beam ofthe LRF to be maintained perpendicular to the shaft after moving betweentwo adjacent axial shaft locations without moving the robot arm 62 abouta vertical axis relative to the base 64.

The method for aligning two rotating shafts which are coaxial coupledtogether using the multi axis robotic arm embodiment of the apparatus 60has an initial step of providing a servo operated multi axis robotic armattachable to a base affixed in spaced relation to axis of two axiallycoupled rotating shafts oriented along a Y-axis. The robotic arm has adistal end pivotably attached to a laser range finder (LRF) to orientthe LRF a distance from the two rotating shafts to measures the locationof a plurality of peripherally spaced spots on the shafts on two axialpositions on each.

A controller is provided, having a processor and memory, communicatingwith the servo motors of the multi axis robotic arm, the LRF and a userinterface. The controller positions the LRF at a first X-axis locationon a first one of the rotating shafts. The controller communicating theservo motors of the multi axis robotic arm, and the X-axis servo to movethe LRF peripherally about the shaft and while storing the LRF locationand the measured distance to a plurality of peripherally spaced spots.

Next the controller positions the LRF at a second X-axis location on thefirst rotating shaft, causing the controller communicating the servomotors of the multi axis robotic arm, to move the LRF peripherally aboutthe shaft and storing the LRF location and the measured distance to aplurality of peripherally spaced spots.

The controller moves the LRF to a third X-axis location on a second oneof the rotating shafts, causing the controller communicating the servomotors of the multi axis robotic arm, to move the LRF peripherally aboutthe shaft and storing the LRF location and the measured distance to aplurality of peripherally spaced spots.

The controller moves the LRF to a fourth X-axis location on the secondrotating shaft, measuring causing the controller communicating the servomotors of the multi axis robotic arm, to move the LRF peripherally aboutthe shaft and storing the LRF location and the measured distance to aplurality of peripherally spaced spots.

With the data collected the controller calculates, in the processor, thecenterline of the two shafts at each of the four X-axis locations usingstored LRF location and the measured distance to a plurality ofperipherally spaced spots, using a best-fit circle algorithm to definetwo spaced apart axis location points for each shaft. The processordetermines the adjustment of one of the two shafts needed to move theshafts in to coaxial alignment. The adjustment information needed toalign the shafts is then output to the user via a user interface.

Another embodiment of the servo operated multi axis positioning device80 is shown in FIG. 15-17. This simple device moves the LRF along the Yand Z axes via a servo motor relative to rotating shaft 84. Shaft centercan be determined using curve fitting as previously described or, in thesimplest form, the shaft diameter and centerline height is determined bylocating the top and bottom edge of the shaft. The Z distance isdetermined by measuring the Z location of the shaft edge and subtractingthe shaft radius. The device is preferably moved along a base betweenfour positions along the X axis by a servo to measure two shaftcenterlines on each of the shafts to be aligned.

While exemplary embodiments are described above, it is not intended thatthese embodiments describe all possible forms of the invention. Rather,the words used in the specification are words of description rather thanlimitation, and it is understood that various changes may be madewithout departing from the spirit and scope of the invention.Additionally, the features of various implementing embodiments may becombined to form further embodiments of the invention.

What is claimed is:
 1. An apparatus for aligning two rotatable shaftswhich are coaxially coupled together, the apparatus comprising: a basewhich is positioned in spaced adjacent orientation to two rotatableshafts which are coaxially coupled together; a servo operated multi axisrobotic arm attachable to a base and supporting a laser range finder(LRF), the robotic arm having a distal end pivotably attached to thelaser range finder (LRF) to orient the LRF a distance from the tworotating shafts to measures the location of a plurality of peripherallyspaced spots on the shafts at two axial positions on each shaft; acontroller communicating with servo motors of the servo operated multiaxis robotic arm and the LRF, the controller having a processorprogrammed to: position the LRF at a first axial location on a first oneof the rotatable shafts, causing the controller communicating the servomotors of the multi axis robotic arm, to move the LRF peripherally aboutthe shaft and storing the LRF location and the measured distance to aplurality of peripherally spaced spots; position the LRF at a secondaxial location on a first one of the rotatable shafts, causing thecontroller communicating the servo motors of the multi axis robotic arm,to move the LRF peripherally about the shaft and storing the LRFlocation and the measured distance to a plurality of peripherally spacedspots; position the LRF at a third axial location on a second one of therotatable shafts, causing the controller communicating the servo motorsof the multi axis robotic arm, to move the LRF peripherally about theshaft and storing the LRF location and the measured distance to aplurality of peripherally spaced spots; position the LRF at a fourthaxial location on the second rotatable shafts, causing the controllercommunicating the servo motors of the multi axis robotic arm, to movethe LRF peripherally about the shaft and storing the LRF location andthe measured distance to a plurality of peripherally spaced spots; andcalculating the centerline of the two shafts at each of the four X-axislocations using stored measurement and spot location data, locating anaxis for each of the two shafts, and determining an adjustment for oneof the two shafts to move the shafts in to coaxial alignment.
 2. Theapparatus of claim 1, wherein the controller is programmed to collect atleast 10 data readings at each spot that data is collected and togenerate an average distance value.
 3. The apparatus of claim 1, whereinthe controller is programmed to collect a least 200 data readings ateach spot that data is collected.
 4. The apparatus of claim 1, whereinthe controller is programmed to calculate the center of the two shaftsat each of the four X-axis locations by fitting a circular segment tothe average collected data for each spot and using the diameter of acircle defined by the circular segment to determine the shaft center ateach axial location.
 5. The apparatus of claim 1, wherein the controlleris programed to orient the LRF perpendicular to the shaft at each spotbeing measured.
 6. The apparatus of claim 1, wherein the controller isprogramed to orient the LRF less than 80 mm from the shaft at the spotsbeing measured.
 7. The apparatus of claim 1, wherein servo operatedmulti axis robotic arm has at least four degrees of freedom controlledby four servo motors.
 8. The apparatus of claim 1, wherein servooperated multi axis robotic arm has at least five degrees of freedomcontrolled by five servo motors.
 9. The apparatus of claim 1, furthercomprising a carriage interposed between a robotic arm and the basewherein the robotic arm mounted on the carriage can slide along the baseparallel to a Z-axis, driven by one of the servo motors, to move betweenat least two positions corresponding to the first and second shafts. 10.The apparatus of claim 9, wherein the robotic arm can move between atleast four positions corresponding to the first, second, third andfourth axial locations on the two shafts.
 11. A method for aligning tworotatable shafts which are coaxially coupled together, the methodcomprising: providing a servo operated multi axis robotic arm attachableto a base affixed in spaced relation to axis of two axially coupledrotating shafts oriented along a X-axis, the robotic arm having a distalend pivotably attached to a laser range finder (LRF) to orient the LRF adistance from the two rotating shafts to measures the location of aplurality of peripherally spaced spots on the shafts at two spaced apartaxial positions on each shaft; providing a controller, having aprocessor and memory, communicating with the servo motors of the multiaxis robotic arm, the LRF and a user interface; positioning the LRF at afirst X-axis location on a first one of the rotating shafts, causing thecontroller communicating the servo motors of the multi axis robotic arm,to move the LRF peripherally about the shaft and storing the LRFlocation and the measured distance to a plurality of peripherally spacedspots; positioning the LRF at a second X-axis location on the firstrotating shaft, axially spaced apart, from the first X-axis location,causing the controller communicating the servo motors of the multi axisrobotic arm, to move the LRF peripherally about the shaft and storingthe LRF location and the measured distance to a plurality ofperipherally spaced spots; positioning the LRF at a third X-axislocation on a second one of the rotating shafts, causing the controllercommunicating the servo motors of the multi axis robotic arm, to movethe LRF peripherally about the shaft and storing the LRF location andthe measured distance to a plurality of peripherally spaced spots;positioning the LRF at a fourth X-axis location on the second rotatingshaft, axially spaced apart from the third X-axis location, causing thecontroller communicating the servo motors of the multi axis robotic arm,to move the LRF peripherally about the shaft and storing the LRFlocation and the measured distance to a plurality of peripherally spacedspots; and calculating in the processor the centerline of the two shaftsat each of the four X-axis locations using stored LRF location and themeasured distance to a plurality of peripherally spaced spots, using abest-fit circle algorithm to define two spaced apart axis locationpoints for each shaft and determining the adjustment of one of the twoshafts needed to move the shafts in to coaxial alignment and outputtingthe adjustment information to the user via the user interface.
 12. Themethod of claim 11 wherein the step of calculating the center of the twoshafts at each of the four axial locations is done by fitting a circularsegment to the collected data and using the diameter of a circle definedby the circular segment to determine the shaft center at each axiallocation.
 13. The method of claim 11 wherein the two rotatable shaftsare associated with a shaft driven rotary machine and a motor, whereinthe method further comprises operating the driven rotary machine and amotor for a period of time sufficient to reach a stable operatingtemperature before measuring distance to the shaft and storing themeasurement and spot location data at each of the four axial positionswhile the driven rotary machine and motor are rotating.
 14. The methodof claim 11 wherein the controller collects at least 200 data readingsat each spot that data is collected and generates and stores an averageor median distance value at each spot.
 15. The method of claim 11,wherein the provided positioning device further comprises proving anX-axis servo motor communicating with the controller, for positioningthe multi axis robotic arm at an axial location on the base using anX-axis servo motor.
 16. The method of claim 11, wherein the step ofcalculating the center of the two shafts at each of the four axiallocations is done by fitting a circular segment to the collected dataand using the diameter of a circle defined by the circular segment todetermine the shaft center at each axial location.
 17. The method ofclaim 11, wherein the two rotatable shafts are associated with a shaftdriven rotary machine and a motor, wherein the method further comprisesoperating the driven rotary machine and a motor for a period of timesufficient to reach a stable operating temperature before measuringdistance to the shaft and storing the measurement and spot location dataat each of the four axial positions while the driven rotary machine andmotor are rotating.
 18. An apparatus for aligning two rotatable shaftswhich are coaxially coupled together, the apparatus comprising: a basewhich is positionable in spaced adjacent orientation to two rotatableshafts which are coaxially coupled together; a vertical guide supportedon the base and movable relative thereto in a longitudinal directionparallel to the axis of the shafts and a transverse directionperpendicular to the shaft axis in plan view by a longitudinal servo anda transverse servo respectively; a laser range finder (LRF) positionablea distance from the two rotating shafts to measures the location of aplurality of vertically spaced spots on the shafts at two axialpositions on each shaft, the LRF movable along the vertical guide by avertical servo; a controller communicating with servo motors of thelongitudinal servo, the transverse servo and the vertical servo, thecontroller having a processor programmed to: position the LRF at a firstlongitudinal location adjacent a first one of the rotatable shafts,causing the servo motors to move the LRF vertically relative the shaftand storing the LRF location and the measured distance to a plurality ofvertically spaced spots; position the LRF at a second longitudinallocation adjacent a first one of the rotatable shafts, causing the servomotors to move the LRF vertically relative the shaft and storing the LRFlocation and the measured distance to a plurality of vertically spacedspots; position the LRF at a third longitudinal location adjacent asecond one of the rotatable shafts, causing the servo motors to move theLRF vertically relative the shaft and storing the LRF location and themeasured distance to a plurality of vertically spaced spots; positionthe LRF at a fourth longitudinal location adjacent a second one of therotatable shafts, causing the servo motors to move the LRF verticallyrelative the shaft and storing the LRF location and the measureddistance to a plurality of vertically spaced spots; and calculate thecenterline of the two shafts at each of the four longitudinal locationsusing stored measurement and spot location data, locating an axis foreach of the two shafts, and determining an adjustment for one of the twoshafts to move the shafts in to coaxial alignment.
 19. The apparatus ofclaim 18 wherein the controller is provided with a user interfaceenabling a user to input the known diameter of the shafts.
 20. Theapparatus of claim 19 wherein the processor is programmed to cause thevertical servo to move the LRF through a range sufficient to enable theprocessor to locate the vertical height center of the shaft and thedistance between the shaft and the LRF and the shaft center therebyproviding a location of the shaft centerline at each of the fourlongitudinal locations.
 21. A method for aligning two rotatable shaftswhich are coaxially coupled together, the method comprising: providing aservo operated multi axis positioning device having at least 3 degreesof freedom attachable to a base affixed in spaced relation to axis oftwo axially coupled rotating shafts oriented along a X-axis, the roboticarm having a distal end pivotably attached to a laser range finder (LRF)to orient the LRF a distance from the two rotating shafts to measuresthe location of a plurality of peripherally spaced spots on the shaftsat two spaced apart axial positions on each shaft; providing acontroller, having a processor and memory, communicating with the servomotors of the multi axis positioning device, the LRF and a userinterface; positioning the LRF at a first X-axis location on a first oneof the rotating shafts, causing the controller communicating the servomotors of the multi axis positioning device, to move the LRFperipherally about the shaft and storing the LRF location and themeasured distance to a plurality of peripherally spaced spots;positioning the LRF at a second X-axis location on the first rotatingshaft, axially spaced apart, from the first X-axis location, causing thecontroller communicating the servo motors of the multi axis positioningdevice, to move the LRF peripherally about the shaft and storing the LRFlocation and the measured distance to a plurality of peripherally spacedspots; positioning the LRF at a third X-axis location on a second one ofthe rotating shafts, causing the controller communicating the servomotors of the multi axis positioning device, to move the LRFperipherally about the shaft and storing the LRF location and themeasured distance to a plurality of peripherally spaced spots;positioning the LRF at a fourth X-axis location on the second rotatingshaft, axially spaced apart from the third X-axis location, causing thecontroller communicating the servo motors of the multi axis positioningdevice, to move the LRF peripherally about the shaft and storing the LRFlocation and the measured distance to a plurality of peripherally spacedspots; and calculating in the processor the centerline of the two shaftsat each of the four X-axis locations using stored LRF location and themeasured distance to a plurality of peripherally spaced spots, using abest-fit circle algorithm to define two spaced apart axis locationpoints for each shaft and determining the adjustment of one of the twoshafts needed to move the shafts in to coaxial alignment and outputtingthe adjustment information to the user via the user interface.